New Laser to Shine Light on Remote Sensing

Research guides to new lasers in the IR (Source: U Adelaide)

Research guides to new lasers in the IR (Source: U Adelaide)

A revolu­tionary new type of laser developed by the University of Adelaide is promising major advances in remote sensing of greenhouse gases. The research team  has shown that the new laser can operate over a large range within the infrared light spectrum. “Most lasers work only at one wavelength of light,” says lead author Ori Henderson-Sapir. What’s special about this laser is that it not only can change wave­lengths, but that it can be tuned over a very large wave­length range.

In fact this laser has the largest wavelength tuning ever demons­trated by a fibre laser, and reaches further into the mid-infrared than ever achieved before from a fibre laser operating at room tempe­rature. Importantly, the laser operates in a wavelength range in which the molecular finger­prints of many organic molecules occur. The finger­prints are patterns of light absorption at different fre­quencies.

“The new laser is operating at a wavelength where many hydro­carbon gases, including the green­house gases, absorb light,” says project leader David Ottaway, from the University of Adelaide’s School of Physical Sciences and the Institute for Photonics and Advanced Sensing. “This means that by changing the wavelength of our laser, we can measure the light absorp­tion patterns of different chemicals with a high degree of sensitivity. This will allow us to detect small concen­trations of these gases at consi­derable distances. Remote detection of greenhouse gasses such as methane and ethane opens up the prospect of differen­tiating between various potential emission sources, such as natural gas extraction and agri­culture — and so pinpoint areas of concern.”

Other potential appli­cations for the future include the possibility of analysing trace gases in exhaled breath at a clinic to detect the presence of disease. For example, acetone can be detected in the breath when someone has diabetes. “The main limitation to date with laser detection of these gases has been the lack of suitable and affordable light sources that can produce enough energy and operate at the correct part of the light spectrum,” says Stuart Jackson of Macquarie University. The few available sources that can cover the wavelength range necessary for the detection of these gases are generally expensive and bulky and, therefore, not suitable for widespread use.

The new laser uses an optical fibre which is easier to work with – less bulky and more portable – and much more cost effective to produce than other types of laser. “It has incre­dible potential for scanning for a range of gases with a high level of sensi­tivity and, because of its afforda­bility, it promises to be a very useful sensing tool,” says Ottaway. “We hope this laser will open up oppor­tunities for lasers in the mid-infrared in a similar manner that that titanium doped sapphire lasers revolu­tionized lasers operating in the visible and near-infrared.”

Reference: O. Henderson-Sapir et al.: Versatile and widely tunable mid-infrared erbium doped ZBLAN fiber laser, Opt. Lett. 41, 1676 (2016), DOI: 10.1364/OL.41.001676

Link: Institute for Photonics and Advanced Sensing (D. Ottaway), University of Adelaide, Australia

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